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Oseltamivir and zanamivir are medications used to treat influenza A and B viruses. The primary effect of the drugs is to reduce the symptoms of influenza, such as fever or chills, body pains, and cough. It may be used to prevent flu for people who have been exposed to carriers of the virus. However, both medications are required to be taken twice a day for five days, compared to a new drug approved in Japan that is taken once a day, which can kill the virus in as little as one day.
Existing Influenza Medications
Oseltamivir or what is popularly known as Tamiflu is an antiviral used to treat and prevent influenza A and B infections. It is highly recommended anti-flu drug in people at high risk of complications within 48 hours of infection. The drug can decrease the risk of pneumonia by up to 44 percent and rate of hospitalization by 63 percent.
Otherwise, the discretion to prescribe oseltamivir depends if the patient is positive for influenza, confirmed by laboratory tests. Patients who only exhibit flu-like symptoms will not benefit from the medication.
“Other researchers examined the same study data and concluded that Tamiflu does not reduce hospitalizations or other complications when analyzing all people who went to the doctor because of flu-like symptoms. This means that if your doctor prescribes Tamiflu without giving you a flu test, it is less likely to help you get better,” said Dr. Margaret Dayhoff-Brannigan of the National Center for Health Research.
Patients who took oseltamivir are likely to recover one day faster than those who did not.
According to the Centers for Disease Control and Prevention, the European Center for Disease Prevention and Control, the Public Health England, and the American Academy of Pediatrics, high-risk patients with complications who are recommended to receive oseltamivir treatment include:
- Children age five years old, particularly children younger than two years old.
- Adults 65 years old and older.
- Pregnant women.
- People who are in nursing homes.
- People who are in long-term care facilities.
- American Indians and Alaska Natives.
- Indigenous peoples of the Americas.
- People with underlying health conditions, such as asthma and diabetes.
As a neuraminidase inhibitor, oseltamivir binds to neuraminidase, an enzyme, on the surface of the virus. The binding effect prevents the new viruses to escape from infected cells, limiting their abundance in the system and giving a better chance for the immune system to kill them.
Zanamivir is also a neuraminidase inhibitor that inhibits reproduction of the virus. Unlike with oseltamivir, zanamivir is used for individuals who are considered healthy before contracting the illness. It is sold as a powder for oral inhalation.
New Drug from Japan
The Japan Health Ministry approved a new drug called baloxavir marboxil developed by Shionogi, for the influenza A and B viruses. The new drug also acts as an inhibitor to suppress the replication of influenza. But unlike with existing drugs, baloxavir marboxil works by inhibiting an enzyme called cap-dependent endonuclease, an essential part of the virus that translates genes into proteins. The disruption of the enzyme makes it difficult for the virus to replicate and makes it harder to enter healthy cells, which causes the influenza symptoms.
In phase 3 clinical trials, the researchers recruited 1494 random participants, aged 12 to 64 years old, who are otherwise healthy, but have been diagnosed with influenza. They tested the new drug in different settings including a direct comparison to oseltamivir and people younger than 20 years old. The findings revealed that baloxavir marboxil can significantly reduce fever and speed up recovery from the illness, compared to the placebo,
“The data that we’ve seen looks very promising. This could be a breakthrough in the way that we treat influenza,” said Martin Howell Friede, the coordinator of the Initiative for Vaccine Research at the World Health Organization.
The clinical trial excluded several criteria including patients with a severe case of influenza, patients allergic to oseltamivir, patients who had another infection, patients with severe underlying diseases, and patients who are at high risk to the potential limitations of the new medication.
Baloxavir marboxil is set to be launched in Japan immediately after the price list from the National Health Insurance has been updated. However, the drug will not receive approval in the United States until 2019.
A new and better vaccine may also be on its way as scientists at the University of California in Los Angeles found a new approach that removes the defense mechanisms of the virus. After studying every the entire genome of the virus for four years, the research team found the evasive functions of influenza.
“By disabling these interferon-evasion functions, the engineered virus is weakened in typical hosts. With this approach, the safety and efficacy requirement of vaccines can potentially be achieved simultaneously. In traditional vaccine development, one is usually sacrificed for the other,” said Yushen Du, the first author of the study at UCLA.
[메디컬리포트=Ralph Chen 기자]